On the same day that two of its power plants were scheduled to undergo surprise safety inspections by an atomic regulator and lawmakers, France received another surprise at its other nuclear sites: Greenpeace activists who broke through security.

According to Al Jazeera [3], activists were able to sneak into the power plant in Nogent-sur-Seine, a commune about 60 miles southeast of Paris. They hung a banner that said "Coucou" ("Hey") and "Facile" ("Easy") on the reactor's containment building.

Some scaled a domed containment building above a nuclear reactor to hoist a banner that read "safe nuclear doesn't exist" and paint an exclamation point, evoking danger, on the rooftop.

Greenpeace said its break-in aimed to show that a review of safety measures—ordered by French authorities after a tsunami ravaged Japan's Fukushima Dai-ichi nuclear plant in March—was focused too narrowly on possible natural disasters and not human factors.

Several hours passed after the nine Greenpeace members at Nogent-sur-Seine were put under custody. At three different nuclear sites in France, security was able to prevent the activists from breaching their site.

However, when the intruders said that there still remained more activists at other nuclear plants, French authorities embarked on a "thorough sweep" across all of the country's 20 power plants, according to The AP.

Bloomberg [5] reported that President Nicolas Sarkozy was later informed of the incident, and said, "It's irresponsible to take risks with their lives and the lives of others."

Still, the stunt worked.

Eric Besson, the French Industry Minister, told France Info radio that they now would have to "take measures so this doesn't happen again." Besson's office also told Bloomberg that the nuclear industry will need to launch an in-depth investigation.

France is a huge consumer of nuclear energy, and obtains nearly three-quarters of the country's electricity from it, according to The AP. Although clashes between activists and industry members are rare, the nuclear industry regularly encounters protests against their shipping of nuclear waste.